192 PRACTICAL ORGANIC CHEMISTRY
Quinone and Qninol (Hydroquinone),
C H ^° and C H /OH 1
C6w4- ancl ^^H
Woskresensky, Annalen^ 1838, 27, 268 ; Nietzki, Ber., 1886,
19, 1467 ; Meyer and Jacobson, Lehrbuch, vol. ii., 421.
25 grms. aniline.
200 „ (no c.c.) cone, sulphuric acid.
750 c.c. water.
80 grms. potassium bichromate.1
The water and aniline are mixed together in a large glass jar
(i^- litres) and the sulphuric acid added. The mixture is cooled
in ice and stirred with a turbine (see Fig. 64, p. 91). The finely-
powdered bichromate is added every few minutes in small quan-
tities on the end of a small spatula, until about one-third has
been added, care being taken that the temperature does not
exceed 10°. The mixture is then left to stand over night, and
the remaining two-thirds of the bichromate introduced as before.
Aniline black separates out in the first part of the operation,
and in the second part of the process gradually dissolves,
giving a deep brown solution. The liquid, after standing for
four to five hours more, is divided into two about equal portions.
One half is shaken up, not too vigorously, with a large quantity
(200 c.c.) of ether three times. The same ether may be distilled
and used again. Vigorous shaking produces an emulsion, which
very slowly separates. On distilling off the ether, the quinone
remains in the form of yellow needle-shaped crystals, which may
be purified by sublimation. The substance is placed in a flask
attached to a condenser, and a rapid current of steam blown
through. The quinone sublimes and collects in the receiver,
and is separated from the water by filtration, and dried. Yield
about 10 grams.
1 Or an equivalent quantity of sodium bichromate (75 grams), which may be
dissolved in 3 — 4 times its weight of water and delivered from a tap-funnej